Bent-out wall in the region of a substantially rectangular burner opening

ABSTRACT

Bent-out wall in the region of a substantially rectangular burner opening ( 2 ), wherein the bent-out wall ( 1 ) is formed by tube walls ( 3 ) and the tube walls ( 3 ) consist of tube-fin-tube combinations welded in a gastight manner and the tubes ( 5 ) thereof are flowed through by a cooling medium, wherein at least part of the bent-out wall ( 1 ) along the two longitudinal sides ( 7 ) of the rectangular burner opening ( 2 ) is formed by means of prefabricated tube wall segments ( 4 ) and wherein the prefabricated tube wall segments ( 4 ) are machine-welded in the planar state at the workshop and are subsequently bent at the workshop to a wall bending radius (R) of 70-140 mm and a wall bending angle (W) of 110°-150°.

The invention relates to a bent-out wall in the region of a substantially rectangular burner opening.

Walls are bent out in tube wall regions of steam generators to which burners are fitted, with which the combustion chamber of the steam generator can be heated, for example with fossil fuels. Amongst other things, round or rectangular burner openings are used, use generally being made of rectangular burner openings in the tube wall regions of a steam generator in the case of large, corner-fired steam generators. The tube walls of a steam generator are generally formed from a tube-fin-tube combination, a cooling medium flowing through the tubes.

In current, modern steam generators, which generally have 8 burner openings per steam generator and outputs of more than 800 MW and an overall height of more than 100 m, the burners and thus also the burner openings are correspondingly also implemented with large dimensions. This places high requirements on the structural solution and the implementation on the production side of the bent-out walls at these burner openings. These burner openings are formed by a tube-fin-tube combination being bent outward out of the planes or the corners of the tube wall or the tube walls of the steam generator, i.e. pointing away from the combustion chamber. The creation of the bent-out walls is carried out in such a way that all the tube bends and fins required for the purpose are prefabricated in individual fabrication, the fins being given a double-bevel seam treatment on both sides for the welding. The bent fins are then welded to the tube bends by hand to form the desired bent-out walls.

As a result of the large burner opening dimensions and the multiplicity of manual welds (tube-fin-tube) and the accumulations of weld material resulting therefrom, the result is increased fabrication inaccuracy, mainly as a result of high levels of weld shrinkage. Likewise, the aforementioned fabrication procedure entails high fabrication expenditure, for example as a result of the need for devices and jigs in order to ensure the dimensional stability and the geometric shape of the bent-out walls. Furthermore, on account of the multiplicity of manual welds, increased expenditure on straightening is unavoidable.

The object of the present invention is to propose a bent-out wall in the region of a substantially rectangular burner opening in which the production and mounting thereof is carried out in an efficient and practicable way. In particular, it is an object of the invention to propose a bent-out wall which provides for simplification of the fabrication with simultaneous reduction in the costs, an increase in the quality and a reduction in the fabrication times and, in particular, is designed in structural terms such that the burner fitted to the burner opening experiences good cooling.

The aforementioned object is achieved by a bent-out wall in the region of a substantially rectangular burner opening as claimed in the entirety of the features of patent claim 1.

Advantageous embodiments of the invention can be gathered from the sub-claims.

By means of the solution according to the invention, a bent-out wall in the region of a substantially rectangular burner opening is devised which has the following advantages:

-   -   the weld shrinkage on the bent-out walls is minimized in the         extreme,     -   the manageability of the fabrication process of the bent-out         walls is increased,     -   the shape accuracy of the design of the bent-out walls is         increased considerably,     -   the fabrication costs of the bent-out walls are reduced,     -   and the fabrication times of the bent-out walls are reduced.

One advantageous development of the invention provides for the wall bending radius R of the bent-out wall to be 100 mm. This ensures that the burner is protected in a most comprehensive way against thermal radiation, the chosen radius representing an optimum in fabrication terms.

In an advantageous embodiment of the invention, the wall bending angle W of the bent-out wall is 135°. In fabrication terms, this angle represents an optimum and protects the burner optimally against thermal radiation.

An expedient development of the invention provides for the prefabricated tube wall segments to have a width of 500 to 1200 mm. This width constitutes an optimum between the desire for few manual welds between the respective prefabricated tube wall segments and the fabrication possibilities on the roll of the bending tool.

Expediently, the tube diameters of the tubes lie between 31.8 mm and 38 mm and the wall thicknesses of the tubes between 4 mm and 7.1 mm. Therefore, from a thermal point of view, the requirements on the steam generator are fulfilled (coolant throughput, etc.) and, secondly, dimensions are proposed which can easily be managed with respect to bending. In a further expedient development, the widths of the fins lie between 10 and 25 mm.

Exemplary embodiments of the invention will be explained in more detail below by using the drawings and the description.

FIG. 1 shows a rectangular burner opening of a steam generator tube wall, illustrated schematically in the view, which is created in the region of the burners by bending out the tube wall (bent-out wall),

FIG. 2 shows a cross-section through the burner opening according to the section “A-A” from FIG. 1, illustrated schematically,

FIG. 3 shows a plan view of a tube wall segment according to the view “B” from FIG. 2, illustrated schematically (plan view rotated through 90°).

FIG. 1 shows a substantially rectangular burner opening 2 of a steam generator tube wall, illustrated schematically, which opening is created by the bent-out wall 1 of the tube wall 3.

According to the invention, at least part of the bent-out wall 1 is formed along the two longitudinal sides 7 of the rectangular burner opening 2 by means of prefabricated tube wall segments 4. The prefabricated tube wall segments 4, which can also be designated tube panels and which are assembled from a combination of tubes 5 and fins 6, are, according to the invention, welded by machine at the workshop and in the planar or flat state (machine welding). A number of tubes 5 and fins 6 are inserted into the apparatus of a tube panel welding machine prepared for the purpose, in order to achieve a desired width of the tube wall segment 4 to be prefabricated. A width of the tube wall segment 4 of 500 to 1200 mm has proven to be advantageous here since, in this case, the number of connecting welds of the prefabricated tube wall segments 4 to be welded to one another manually can be kept small and this width range can be managed well in the tube panel welding machine and later during mechanical bending. In order to achieve the desired spacing from tube 5 to tube 5 (tube pitch within a tube wall), all the fins 6 are calibrated in terms of their width before they are welded to the tubes 5 by means of the tube panel welding machine. As a result of the calibration of the fins 6, the complicated machining of the double-groove weld bevel onto these fins, which otherwise would be necessary during manual welding, is advantageously dispensed with.

Following the machine welding of the tubes 5 and fins 6 to form a planar tube wall segment 4, according to the invention the whole of the latter is bent by machine at the workshop by means of a tube wall bending machine to a wall bending radius R of between 70 and 140 mm and a wall bending angle W of between 110° and 150°, wherein the tube wall segment 4 is preferably bent with a wall bending radius R of 100 mm and further preferably with a wall bending angle W of 135° (see FIGS. 2 and 3). The wall bending angle W is to be understood to mean that one end of the prefabricated tube wall segment 4 is bent through preferably 135° with respect to the other end of the tube wall segment 4, which means that an enclosed angle of preferably 45° is produced between the two ends of the tube wall segment 4.

As a result of the prefabrication according to the invention of machine-welded tube wall segments 4, a geometrically accurately defined shape is produced which, following subsequent bending, maintains this geometric shape accuracy, and thus each of the prefabricated tube wall segments 4 represents a dimensionally accurate and fixed reference point within the entire bent-out wall 1.

Since the tube wall segments 4 have fixed pitches as a result of the calibration of the fins 6 before the welding in the welding machine, up to 95% of the manual welds, which are responsible for the weld shrinkage, primarily transversely with respect to the tube axis, are dispensed with. Thus, the machine-welded and subsequently bent tube wall segments 4 contribute to managing the dimensional and shape deviations within the bent-out walls 1 that otherwise occur and are caused by weld shrinkage.

The tubes 5 of the tube wall segments 4 of the bent-out wall 1 according to the invention have, for example, tube external diameters of 31.8 to 38 mm and wall thicknesses of 4 to 7 mm. The fins 6 inserted between the tubes 5 of the bent-out wall 1 according to the invention have, for example, widths of 10 to 25 mm.

By means of the bent-out wall 1 according to the invention and the specific geometry thereof, in addition to the advantages in terms of fabrication, extensive cooling and protection against thermal radiation of the burner fitted to the burner opening 2 of the bent-out wall 1 is also ensured. This is also achieved specifically by the narrow wall bending radius R.

LIST OF DESIGNATIONS

-   1 Bent-out wall -   2 Burner opening -   3 Tube wall -   4 Tube wall segment -   5 Tube -   6 Fin -   7 Longitudinal sides of the rectangular burner opening 

1. A bent-out wall in the region of a substantially rectangular burner opening, wherein the bent-out wall is formed by tube walls and the tube walls consist of tube-fin-tube combinations welded in a gastight manner and a cooling medium flows through the tubes thereof, wherein at least part of the bent-out wall is formed along the two longitudinal sides of the rectangular burner opening by means of prefabricated tube wall segments, and wherein the prefabricated tube wall segments are machine-welded in a planar state and subsequently bent to a wall bending radius (R) of 70 to 140 mm and a wall bending angle (W) of 110° to 150°.
 2. The bent-out wall in claim 1, Wherein the wall bending radius (R) is 100 mm.
 3. The bent-out wall in claim 1, Wherein the wall bending angle (W) is 135°.
 4. The bent-out wall in claim 1, Wherein the tube wall segments have a width of 500 to 1200 mm.
 5. The bent-out wall in claim 1, Wherein the tube walls comprise a diameter between 31.8 mm and 38 mm and a thickness between 4 mm and 7.1 mm.
 6. The bent-out wall in claim 1, wherein the fin comprises a width between 10 mm and 25 mm. 